This section provides background information related to the present disclosure which is not necessarily prior art.
Exhaust sampling systems are conventionally used in conjunction with engines or vehicles with internal combustion engines to determine the mass of pollutants produced by the engine during use. Such exhaust sampling systems may include a constant volume sampler (CVS) or a bag mini-diluter (BMD) that extract diluted exhaust gas for analysis in an effort to determine the pollutant mass of the particular engine.
During operation of a CVS system, for example, engine exhaust is diluted with a diluent gas, and a sample of the diluted exhaust is proportionally extracted and stored in one or more sample bags. Depending on the engine or vehicle size, drive or duty cycle, and ambient conditions, the CVS total flow rate, which includes both the diluent gas and engine exhaust, is selected to ensure the diluted exhaust sample does not condense water when extracted during sampling, stored in the bags, or analyzed after the test phase. Once the sample bags are filled with diluted exhaust gas, the contents of the sample bags may be analyzed to determine the pollutant mass over the test phase for the particular engine.
Vehicles incorporating traditional combustion engine powertrains continuously operate an internal combustion engine of the powertrain and, as a result, an internal combustion engine associated with a conventional vehicle powertrain is continuously operated during a test phase. As a result, collection of the diluted exhaust by the CVS system is likewise continuous throughout the test phase.
New powertrains are being developed, however, that intermittently use an internal combustion engine during operation of a vehicle. For example, a hybrid-electric vehicle may only use an internal combustion engine when recharging a battery of the vehicle. Such powertrains pose challenges for both CVS sampling systems and BMD sampling systems, as each system is conventionally configured to sample (i.e., collect) for analysis a diluted exhaust gas from an internal combustion engine that operates during an entire sample phase.